Originally Posted By: Garak
Not being a formulator, I'm not sure I can answer that without being terribly circular.
I would say that would include being able to meet the SM (or whatever S spec is met). Of course, that doesn't really answer anything. I think the main contrasts you would see would be if you looked at something like a two-stroke diesel lube, whose elemental analyses are very, very different from what you'd see in a normal HDEO or PCMO. The two-stroke diesel oils whose analyses I've read have very low zinc content, if I remember correctly.
Obviously, too, in a dual rated oil, the specifications are shown as CJ-4/SM, and certain limitations (i.e. phosphorous) are handled differently than a normal SM or higher, even in a 30 grade. A 10w-30 CJ-4/SM can have more phosphorous content than, say, even a 10w-30 SM, even if the latter weren't GF-4. How much higher the limits are, I'm not sure, but if you put me on the spot, I'd suggest a couple hundred ppm.
Ok thanks!
what about CJ-4 only rated diesel oils... would they not contain high zinc content ?
and in this case, even if SM is not mentioned in its specs, would this CJ-4 rated oil not suffice the base oil requirements of almost any gasoline engine (with the exception of, perhaps, only a few most modern hybrid engines) ?